As the mid-Atlantic rift opened some 24 million years ago, magma began to pour out at the bottom of the ocean. It spread across the sea floor in what is now the north Atlantic Ocean. But it took millions of years for volcanoes to reach the surface.

Iceland, with about 200 post-glacial volcanoes, is one of the most active volcanic countries on the planet. On average, there’s an eruption every fifth year in the country. And back in historic times, one third of all lava that has flowed out on planet Earth has erupted to the surface in Iceland.

But even when there are no volcanic eruptions in Iceland, the entire area is a geothermal hotspot. And geothermal events can communicate to scientists where there are still bodies of magma close to the surface of the earth, still cooling down, hundreds or thousands of years after an eruption.

For Bjorn Oddsson, geothermal events are significant, because they can melt the large glaciers that cover some of the biggest volcanoes in Iceland. When glaciers start melting, pressure is lifted from volcanoes, increasing the risk of eruptions.

Who can forget late March, 2010, when lava sputtered from a small volcano – Eyjafjallajokul – and moved into Iceland’s lower valley. Located within one of the busiest flight corridors in the world, the eruption of ash clouds travelled all over Europe, quickly catching everyone’s attention. Flight cancellations, air traffic complications followed, and the airline/tourism industry lost more than four billion dollars. And then – quite suddenly – the eruption stopped five weeks later.

Was this the volcano’s temporary reprieve, or a hint of catastrophic problems to come? Can scientists learn to predict eruptions and understand why some eruptions are more violent than others?

Scientists are working to understand Icelandic eruptions. Follow a research them as they travel inside a living volcano, repel into a dark void 450 feet straight down, and examine a magma chamber once filled with red hot magma…Watch Into Iceland’s Volcano on Thursday, April 7th at 9 PM et/pt on the National Geographic Channel!